The present invention relates to limited slip differentials, and more particularly, to such differentials of the type having means for retarding differentiating action, and actuating means for actuating the retarding means.
Limited slip differentials of the type to which the present invention relates typically include a gear case defining a gear chamber and disposed therein a differential gear set including at least one pinion gear and a pair of bevel side gears. A clutch pack is typically disposed between each of the side gears and the adjacent surface of the gear case, such that the clutch pack is operable to retard rotation between the gear case and the side gears.
In many limited slip and/or locking differentials, some sort of actuating mechanism is provided to actuate or move the clutch pack to its engaged condition. One of the current trends in the field of vehicle traction modifiers involves the desire to be able to actuate the clutch packs in response to an external signal, rather than in response to the sensing of a predetermined speed differential as has typically been the case in the prior art.
A typical prior art limited slip differential, actuated in response to an external fluid pressure signal, is illustrated in U.S. Pat. No. 2,991,664. Although it is considered possible to produce a somewhat satisfactory limited slip differential in accordance with the teachings of the prior art, there are distinct disadvantages of the prior art design which limit its commercial desirability. In the cited prior art, the clutch pack is actuated by a pressure-actuated piston, disposed adjacent the end of the clutch pack. Therefore, it is necessary to communicate the external fluid pressure signal into the differential gear case, thus requiring rotating seals. In addition, the hydraulic pressure acting on the clutch pack is acting in opposition to the gear reaction forces which inherently occur during differentiation. The result is a need for an even greater fluid pressure, further increasing the likelihood of fluid leakage.
Another disadvantage is that most limited slip differentials would need major redesign of the gear case and associated structure in order to utilize an actuation means of the general type shown in the cited reference.